Quentin Tarantino’s deeply personal, ’60s-cool, darkly funny, trippy, bold and sensational “Once Upon a Time in Hollywood” is filled with pitch-perfect vignettes perfectly capturing the vast chasm in the country and in the world of American pop culture in 1969.

This is a brilliant and sometimes outrageously fantastic mashup of real-life events and characters with pure fiction. It’s also a fractured fairy tale. (After all, it IS called “Once Upon a Time in Hollywood.”) And it is absolutely dripping with pop-culture touchstones and a flood of references to other movies, on a level exhilarating and borderline overwhelming.

Do you have to “get” every reference? Absolutely not. (But it’s great fun if you do.) For all its deep drilling into the popular culture of the time, for all of its poetic license, “Once Upon a Time” also tells the familiar Hollywood tale of rising stars and fading stars in a changing industry.

It’s also a modern-day Western about an actor who starred on a TV Western and is reduced to guest-starring on a pilot for a Western starring a new up-and-comer.

In one of the great buddy-pairings of the decade, Leonardo DiCaprio and Brad Pitt play Rick Dalton and Cliff Booth, who have been best friends since Rick starred in a late 1950s TV show called “Bounty Law” and Cliff was his stunt double. That’s as good as it got and the closest Rick came to feature film glory wasn’t very close at all.

No longer in demand as a lead, Rick has been playing heavies on a series of episodic TV shows, while Cliff has had to transition from stuntman to Rick’s driver/assistant/handyman/you name it.

Rick lives in a house on Cielo Drive in Benedict Canyon. He has yet to meet the new next-door neighbors — the red-hot film director Roman Polanski (Rafal Zawierucha) and his girlfriend, actress Sharon Tate (Margot Robbie) — but as he tells Cliff, he’s hoping for an introduction at some point because you never know, it could lead to Rick appearing in the next movie by the director of “Rosemary’s Baby.”

We’re never far from the world of movies and TV (and particularly Westerns) in this movie, even when the story takes us to the Charles Manson compound, which was on the old Spahn Ranch in Los Angeles County. An extended sequence set on the ranch is chilling and tense, and then something else, and I’ll say no more.

In typical Tarantino fashion, “Once Upon a Time” features a bounty of colorful cameos, including appearances by QT favorites such as Kurt Russell, Michael Madsen, Bruce Dern and Zoe Bell; Al Pacino as a bottom-feeder agent lobbying Rick to revive his career by doing spaghetti Westerns; Lena Dunham and Dakota Fanning as two of Charles Manson’s zombie disciples; Damian Lewis as Steve McQueen, and the late Luke Perry in his final film role as an actor whose career path briefly intersects with Rick’s. Margaret Qualley is a standout as a fictional Manson girl who catches Cliff’s attention.

DiCaprio strikes just the right seriocomic notes as Rick, who is more than a little narcissistic and kind of an idiot but earns our sympathy because he wears his heart on his sleeve and he truly cares about his friend Cliff.

And then there’s Mr. Pitt. Who kills it.

Some 26 years after his stoner-classic scenes in the Tarantino-scripted “True Romance” and a decade after starring in Tarantino’s “Inglourious Basterds,” Pitt turns in one of the most memorable performances of his career as the badass and fearless, albeit deeply flawed, antihero Cliff. In a movie filled with sparkling acting, Pitt dominates.

It’s one of the best performances of the year in one of the best movies of the year.